Three-dimensional polymer composite parts can be manufactured using different methods, one of which is autoclave molding. In the autoclave molding method, a fabric, usually composed of carbon fibers, is pre-impregnated with a resin matrix. Prepregs are typically laid in a mold and then heated under vacuum to cure the impregnated resin and create the final composite part. The prepregs to be molded into a composite have the advantage of ease of use and high reliability. However, they also have the disadvantage of having limited drapability (i.e. ability to drape).
Another composite manufacturing method is liquid molding. Resin Transfer Molding (RTM) and Vacuum-assisted Resin Transfer Molding (VARTM) are some specific examples. In liquid molding processes, layers of dry reinforcement fibers (without matrix resin) is shaped and compacted into a cohesive, shaped structure called a “preform”. This preform is then infused with an uncured liquid resin, often in a closed mold or enclosed vacuum bag. After the resin infusion stage is completed, the resin is cured resulting in a solid composite part. Liquid molding technology is especially useful in the manufacturing complex-shaped structures which are otherwise difficult to manufacture using conventional prepreg technologies. Moreover, dry, flexible fibrous materials used for forming preforms can have significant advantages over standard, resin-impregnated prepreg materials due their longer shelf life and applicability to more complex geometries.